Thin film lithium-ion battery

ABSTRACT

A thin film lithium-ion battery unit includes a positive current collecting substrate, a positive electrode active material layer on an inner surface of the positive current collecting substrate, a negative current collecting substrate, a negative electrode active material layer on an inner surface of the negative current collecting substrate, a separator between the positive electrode active material layer and the negative electrode active material layer, and electrolyte retained at least in the separator. The positive electrode active material layer, the separator and the negative electrode active material layer constitute a laminated electric core. An outer conductive frame is spaced apart from the positive current collecting substrate and encompasses the positive current collecting substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No.61/837,195, filed Jun. 20, 2013, which is included in its entiretyherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to batteries. More particularly,the present invention relates to a thin film lithium-ion battery.

2. Description of the Prior Art

Lithium-ion secondary batteries or lithium-ion batteries have been usedas power supplies for personal computers, portable devices such as cellphones, cameras, electric tools, and the like. In secondary batteries,the electron producing and consuming reactions are for the most partreversible, and therefore such a battery can be cycled between a chargedand discharged state electrochemically.

When the rechargeable battery is charged, ions formed of the cathodematerial pass from the cathode through the electrolyte to the anode, andwhen the battery is discharged these ions travel back from the anodethrough the electrolyte to the cathode. For example, in batteries havinga cathode comprising lithium, such as a LiCoO₂ or LiMnO₂ cathode,lithium species originating from the lithium-containing cathode travelfrom the cathode to the anode and vice versa during the charging anddischarging cycles, respectively.

FIG. 1 illustrates a conventional structure of a lithium-ion battery. Asshown in FIG. 1, the lithium-ion battery 1 includes an electrochemicalcell comprising an anode active material layer 11 disposed on one sidesurface of a separator 10, a cathode active material layer 21 disposedon the other side surface of the separator 10, an anode currentcollector 12, and a cathode current collector 22. The separator 10 maybe made of polymers such as polyimide (PI), polyprolene (PP),polyethylene (PE), polyvinyl chloride (PVC) or polycarbonate (PC) havingporous structure to only allow the passage of the lithium ions, whilepreventing internal shorting between the anode active material layer 11and the cathode active material layer 21. To electrically connect theanode current collector 12 and the cathode current collector 22 to anexternal circuit or device, the lithium-ion battery 1 may furtherinclude two outwardly extended tabs 12 a and 22 a.

Typically, the separator 10, the anode active material layer 11 and thecathode active material layer 21 are wetted with a liquid electrolytesolution or gel electrolyte. The electrochemical cell is typicallyenclosed in a parallelepipedic metal case 20 such as an aluminum case ina gas-tight manner with a sealant layer 24 securely sealing a gapbetween the tabs 12 a and 22 a.

FIG. 2 illustrates another form of a lithium-ion battery known in theart. As shown in FIG. 2, the lithium-ion battery 3 is integrated with acircuit substrate 30 such as a copper clad laminate (CCL) substrate. Thebase dielectric of the CCL substrate may include polyimide (PI),polyethylene terephthalate (PET) or glass fiber. The circuit substrate30 includes a separator portion 30 a having therein a plurality ofthrough holes or porous structures for the passage of lithium ions. Theseparator portion 30 a is sandwiched by a pair of electrodes 41 and 51.A current collector 42 is disposed directly on a top surface of theelectrode 41. The electrode 41 is sealed by a packaging unit 43.Likewise, a current collector 52 is disposed directly on a top surfaceof the electrode 51. The electrode 51 is sealed by a packaging unit 53.Both of the current collectors 42 and 52 are typically made of expensiveCCL substrates. The use of CCL substrates increases manufacturingcost/complexity and battery weight.

Portable electronic devices have been progressively reduced in size andweight and improved in performance. It is therefore required to developa rechargeable lithium-ion battery or lithium-ion secondary cell havinga high energy density and a high output, which is also cost-effective.Further, after being stored or circled for certain numbers, gas may begenerated in lithium-ion batteries, especially at high temperature,which will reduce life span of the lithium-ion battery. What is needed,therefore, is to provide a lithium-ion battery which has desirable lifespan.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an improved thin filmbattery that is cost-effective, and has simple structure, high capacity,desirable life span and cycle performance.

Another object of the present invention is to provide a thin filmbattery with improved ability of gas resistance and moisture resistance.

According to one embodiment, a thin film lithium-ion battery unitincludes a positive current collecting substrate, a positive electrodeactive material layer coated on an inner surface of the positive currentcollecting substrate, a negative current collecting substrate, anegative electrode active material layer coated on an inner surface ofthe negative current collecting substrate, a separator sandwichedbetween the positive electrode active material layer and the negativeelectrode active material layer, and electrolyte retained at least inthe separator. The positive electrode active material layer, theseparator and the negative electrode active material layer constitute alaminated electric core.

An outer conductive frame is provided to encompass the positiveelectrode active material layer with a gap formed therebetween. Theouter conductive frame is substantially flush with the positive currentcollecting substrate. According to one embodiment of the presentdisclosure, the outer conductive frame may have an opening foraccommodating a positive tab that juts out from an edge of the positivecurrent collecting substrate. According to one embodiment of the presentdisclosure, the outer conductive frame may have a protruding negativetab. A glue layer may be provided to fill the gap.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments, and are incorporated in and constituteapart of this specification. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples. In the drawings:

FIG. 1 illustrates a conventional structure of a lithium-ion battery;

FIG. 2 illustrates another form of a lithium-ion battery known in theart;

FIG. 3 is a schematic top view of an exemplary thin-film lithium-ionbattery according to one embodiment of the invention;

FIG. 4 is a cross-sectional diagram taken along line I-I′ in FIG. 3;

FIG. 5A and FIG. 5B show another embodiment wherein only the seal layeris used;

FIGS. 6A-6D show some variations of the moisture-proof and air-proofpackaging structure according to some embodiments of the invention;

FIG. 7 is a schematic, cross-sectional diagram illustrating a stackstructure of a thin-film lithium-ion battery according to anotherembodiment of the invention;

FIG. 8A and FIG. 8B show irregular outline of the battery cell;

FIG. 9 and FIG. 10 illustrate another embodiment of the presentinvention, wherein FIG. 10 is a cross-sectional view taken along lineII-II′ of FIG. 9.

FIG. 11 shows two battery terminal pairs in one the battery cell;

FIGS. 12A-12D show various approaches to sealing the battery cell;

FIG. 13A and FIG. 13B show a non-rectangular, terraced batterystructure;

FIGS. 14A and 14B show multi-cell batteries according to otherembodiments; and

FIG. 15 illustrates the manufacturing steps for a three-cell in seriesbattery pack.

It should be noted that all the figures are diagrammatic. Relativedimensions and proportions of parts of the drawings are exaggerated orreduced in size, for the sake of clarity and convenience. The samereference signs are generally used to refer to corresponding or similarfeatures in modified and different embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are given toprovide a thorough understanding of the invention. It will, however, beapparent to one skilled in the art that the invention may be practicedwithout these specific details. Furthermore, some well-known systemconfigurations and process steps are not disclosed in detail, as theseshould be well-known to those skilled in the art.

Likewise, the drawings showing embodiments of the apparatus aresemi-diagrammatic and not to scale and some dimensions are exaggeratedin the figures for clarity of presentation. Also, where multipleembodiments are disclosed and described as having some features incommon, like or similar features will usually be described with likereference numerals for ease of illustration and description thereof.

The following sets forth a detailed description of a mode for carryingout the invention. The description is intended to be illustrative of theinvention and should not be taken to be limiting. It is understood thatpresent invention may be applicable to both primary batteries andsecondary batteries, although some embodiments take the secondarybattery as an example.

Please refer to FIG. 3 and FIG. 4. FIG. 3 is a schematic top view of anexemplary thin-film lithium-ion battery according to one embodiment ofthe invention. FIG. 4 is a cross-sectional diagram taken along line I-I′in FIG. 3. As shown in FIG. 3 and FIG. 4, the lithium-ion battery unit100 comprises a positive current collecting substrate 102, a positiveelectrode active material layer 111 coated on an inner surface of thepositive current collecting substrate 102, a negative current collectingsubstrate 104, a negative electrode active material layer 113 coated onan inner surface of the negative current collecting substrate 104, aseparator 112 sandwiched between the positive electrode active materiallayer 111 and the negative electrode active material layer 113, andelectrolyte (not explicitly shown) retained at least in the separator112. The positive electrode active material layer 111, the separator 112and the negative electrode active material layer 113 constitute alaminated electric core 110. The separator 112 between the positive andnegative electrodes prevents physical contact of the electrodes whileenabling ionic transport.

An outer conductive frame 105, which is spaced apart from the positivecurrent collecting substrate 102, may be provided to encompass thepositive current collecting substrate 102 with a gap 125 formedtherebetween. The outer conductive frame 105 is substantially flush orcoplanar with the positive current collecting substrate 102. The outerconductive frame 105 and the positive current collecting substrate 102are formed in the same horizontal level. According to one embodiment ofthe present disclosure, the outer conductive frame 105 is not a closedloop shaped frame and may have an opening 115 for accommodating apositive tab 102 a that juts out from an edge of the positive currentcollecting substrate 102. According to one embodiment of the presentdisclosure, the outer conductive frame 105 may have a protrudingnegative tab 105 a. A glue layer 130 may be provided to fill the gap125. The glue layer 130 is flush with a covering insulation layer 132that covers the outer conductive frame 105 and the positive currentcollecting substrate 102. On the bottom surface of the negative currentcollecting substrate 104, a covering insulation layer 142 may beprovided. The covering insulation layers 132 and 142 may comprisepolyimide (PI), polyvinyl chloride (PVC), polypropylene (PP),polyethylene (PE), polycarbonate (PC), polyurethane (PU), orpolyethylene terephthalate (PET), but not limited thereto. The laminatedelectric core 110 may be sealed by a sealant layer 122 provided alongthe periphery of the laminated electric core 110 between the positivecurrent collecting substrate 102 and the negative current collectingsubstrate 104. A conductor layer 124 may be provided adjacent to thesealant layer 122 by using welding, soldering, or any suitabletechniques.

According to one embodiment of the present disclosure, the outerconductive frame 105 may be electrically coupled to the underlyingnegative current collecting substrate 104 through the conductor layer124. However, in another embodiment, the layer 124 may be composed ofnon-conductive materials such as an adhesive material. It is to beunderstood that other approaches may be used to accomplish theelectrical connection between the negative current collecting substrate104 and the outer conductive frame 105.

FIG. 5A and FIG. 5B show such embodiment. As shown in FIGS. 5A and 5B,the periphery of the laminated electric core 110 between the positivecurrent collecting substrate 102 and the negative current collectingsubstrate 104 is sealed by using only the sealant layer 122. Toelectrically connect the negative current collecting substrate 104 withthe outer conductive frame 105, an extension portion 105 b of the outerconductive frame 105 and an extension portion 104 b of the negativecurrent collecting substrate 104 may be provided. A conductive layer 126may be applied between the extension portion 105 b and the extensionportion 104 b to electrically connect the negative current collectingsubstrate 104 with the outer conductive frame 105.

The shape of the battery cell as set forth in the figures is only forillustration purposes. It is not necessary that the outline of thebattery cell has a rectangular shape as depicted in FIGS. 3 and 5A. Inother embodiments, the outline of the battery cell may have an irregularshape, when viewed from the above, as shown in FIG. 8A. FIG. 8B shows abattery cell having an irregular shape and outline. In addition, athrough opening 310 may be provided. The through opening 310 extendsthrough the entire thickness of the battery cell.

FIG. 9 and FIG. 10 illustrate another embodiment of the presentinvention, wherein FIG. 10 is a cross-sectional view taken along lineII-II′ of FIG. 9. As shown in FIG. 9 and FIG. 10, the outer conductiveframe 105 is a closed loop. An interconnect layer 154 is formed on thecovering insulation layer 132 and is electrically connected to thepositive current collecting substrate 102 through the via plug 152. Thevia plug 152 may comprise conductive pastes, plated copper, solderpastes or other suitable conductive materials known in the art. Theinterconnect layer 154 may extend beyond the outer conductive frame 105to form a positive connecting tab 154 a. Likewise, the outer conductiveframe 105 may also extend beyond the edge of the cell to form a negativeconnecting tab 105 a. The positive connecting tab 154 a and the negativeconnecting tab 105 a form a battery terminal pair.

It is to be understood that the number of the battery terminal pairdepends upon the design requirements and one battery cell may havemultiple battery terminal pairs. As shown in FIG. 11, the battery cellcomprises two battery terminal pairs 150 and 160. The battery terminalpair 150 comprises positive connecting tab 154 a and the negativeconnecting tab 105 a. Likewise, as previously described, the positiveconnecting tab 154 a of the interconnect layer 154 is formed on thecovering insulation layer 132 and is electrically connected to thepositive current collecting substrate 102 through the via plug 152. Thebattery terminal pair 160 comprises positive connecting tab 164 a andthe negative connecting tab 105 b. The positive connecting tab 164 a ofthe interconnect layer 164 is formed on the covering insulation layer132 and is electrically connected to the positive current collectingsubstrate 102 through the via plug 162. In addition to the interconnectlayers 154 and 164, it is to be understood that other circuit patternsor circuit elements may also be formed on the covering insulation layer132.

The glue layer 130 is optional. For example, in FIG. 12A, the coveringinsulation layer 132 directly fills into the gap 125. In FIG. 12B, thegap 125 is filled with the sealant layer 122 that is extruded whenassembling the battery cell. In FIG. 12C, the glue layer 130 mayprotrude from an upper end of the gap 125 and covers a portion of theouter conductive frame 105 and a portion of the positive currentcollecting substrate 102. In FIG. 12D, the glue layer 130 is covered bythe covering insulation layer 132.

According to one embodiment of the present disclosure, the lithium-ionbattery 100 may have a thickness T ranging between 0.25 mm and 0.5 mm,but not limited thereto. In some cases that the battery 100 comprisesfolded cells, thickness may reach 2 mm.

The sealant layer 122, in combination with the conductor layer 124,satisfactorily protects the laminated electric core 110 from exposure toair or moisture. The disclosed structure provides high moisture-proofcapability and insulating property.

FIGS. 6A-6D show some variations of the moisture-proof and air-proofpackaging structure according to some embodiments of the invention.

As shown in FIG. 6A, an air gap 123 may be provided between the sealantlayer 122 and the outer, peripheral conductor layer 124. The air gap 123may be vacuumed in one embodiment. According to another embodiment, dryair or dry inert gas may be filled into the air gap 123.

Alternatively, as shown in FIG. 6B, the peripheral ends of the currentcollecting substrates may be pressed together or pressed toward eachother to form a tapered cross-sectional profile of the periphery of thebattery cell. In this case, both of the sealant layer 122 and theconductor layer 124 have a trapezoid shaped cross section.

In FIG. 6C, the conductor layer 124 is omitted. The outer conductiveframe 105 and the negative current collecting substrate 104 are weldedtogether.

In FIG. 6D, the conductor layer 124 is omitted. Only the seal layer 122is used to seal the periphery of the electric core 110. The peripheralends of the current collecting substrates may be pressed together orpressed toward each other to form a tapered cross-sectional profile ofthe periphery of the battery cell. In this case, the sealant layer 122has a trapezoid shaped cross section.

The positive current collecting substrate 102 may be any one well knownin the art such as an aluminum foil. The positive electrode activematerial layer 111 may comprise a positive electrode active substanceand an adhesive, in which the positive electrode active substance may beany one known in the art for the lithium ion battery. According to someembodiments of the present disclosure, the positive electrode activesubstance may comprise LiCoO₂, LiFePO₄, LiMn₂O₄, or any suitablethree-component substances known in the art. The adhesive may be any onewell known in the art such as polyvinylidene fluoride (PVDF). Accordingto some embodiments of the present disclosure, the positive electrodeactive material layer may also comprise positive electrode additives.The positive electrode additive may be any one well known in the art andmay be selected from conductive agents, for example, at least one ofacetylene black, conductive carbon black and conductive graphite.

The negative current collecting substrate 104 may be any one well knownin the art such as copper foil. The negative electrode active materiallayer 113 may comprise a negative electrode active substance and anadhesive. The negative electrode active substance may be any onecommonly used in lithium ion batteries, such as natural graphite andartificial graphite. The adhesive may be any one well known in the artsuch as polyvinylidene fluoride (PVDF) and polyvinyl alcohol.

The electrolyte may comprise a lithium salt electrolyte and solvent. Insome cases, gel-type or solid state electrolytes may be used. Thelithium salt electrolyte may be at least one selected from lithiumhexafluorophosphate (LiPF₆), lithium perchlorate (LiClO₄), lithiumtetrafluoroborate (LiBF₄), lithium hexafluoroarsenate (LiAsF₆), lithiumhalide, lithium aluminum tetrachloride and lithium fluoro-alkylsulfonate. The solvent may comprise an organic solvent, such as amixture of chain-like acid esters or cyclic acid esters. The chain-likeacid ester may comprise at least one selected from dimethyl carbonate(DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), dipropyl carbonate (DPC) and otherfluorine-containing, sulfur-containing or unsaturated bond-containingchain-like organic esters. Alternatively, a solid state electrolyte suchas lithium phosphorus oxynitride (also known as LiPON) may be used.

The separator 112 is electrically insulated and also has goodelectrolyte retaining performance. According to some embodiments of thepresent disclosure, the separator may be any kind of separators used inlithium-ion batteries known in the art, such as polyolefin micro-porousmembrane, polyethylene felt, glass fiber felt or ultrafine glass fiberpaper. Alternatively, an adhesive resin layer (not shown) may beprovided to bond the positive electrode active material layer 111 ornegative electrode active material layer 113 to the separator 112. Theadhesive resin layer may have a large number of through holes thatcommunicate the positive electrode active material layer 111 or negativeelectrode active material layer 113 with the separator 112. The adhesiveresin layer may create an intimate interfacial contact between adjacentlayers.

FIG. 7 is a schematic, cross-sectional diagram illustrating a stackstructure of a thin-film lithium-ion battery according to anotherembodiment of the invention. The stack structure of a thin-filmlithium-ion battery may be composed of several secondary cells asdescribed above in parallel to increase the discharge currentcapability, and may be available in series packs to increase the totalavailable voltage.

As shown in FIG. 7, the stacked thin-film lithium-ion battery 200 maycomprise at least two lithium-ion battery units 100 a and 100 b, each ofwhich has a structure that is similar to FIG. 4. For example, the upperlithium-ion battery unit 100 a comprises a laminated electric core 110 acomprising a positive electrode active material layer 111 a coated on afirst surface of an intermediate current collecting substrate 203, aseparator 112 a sandwiched between the positive electrode activematerial layer 111 a, and a negative electrode active material layer 113a. On the second surface of the intermediate current collectingsubstrate 203 is the laminated electric core 110 b of the lowerlithium-ion battery unit 100 b. The laminated electric core 110 bcomprises a positive electrode active material layer 111 b coated on thesecond surface of an intermediate current collecting substrate 203, aseparator 112 b sandwiched between the positive electrode activematerial layer 111 b, and a negative electrode active material layer 113b. The laminated electric core 110 a and the laminated electric core 110b are sandwiched between an upper current collecting substrate 202 and alower current collecting substrate 204. Likewise, sealant layers 122 a,122 b and outer packaging layers 124 a, 124 b may be employed to providehigh moisture-proof capability and insulating property.

The layers in the stack structure as described in FIG. 7 may havedifferent dimensions according to another embodiment of the invention.As shown in FIG. 13A and FIG. 13B, the topmost layer 110 a has adimension that is smaller than the underlying layer 110 b, which issmaller than the layer 110 c, which is smaller than the layer 110 d. Thelayer stack forms a non-rectangular or an irregular shape, terracedstructure and may have a rounder corner. By providing suchnon-rectangular configuration of the battery, the free space within aportable electronic device can be efficiently utilized.

FIG. 14A shows a two-cell battery according to yet another embodiment.As shown in FIG. 14A, the two cells including two laminated electriccores 110 a and 110 b may be arranged in parallel to each other on thenegative current collecting substrate 104 and then folded to sandwichabout the positive current collecting substrate 102. The battery is thensealed by using sealant layers 122. The two cells in FIG. 14A areelectrically coupled in parallel. FIG. 14B shows a four-cell batteryaccording to yet another embodiment. As shown in FIG. 14B, the negativecurrent collecting substrate 104 and the four cells including fourlaminated electric cores 110 are folded in a zigzag manner. The fourcells in FIG. 14B are electrically coupled in parallel.

FIG. 15 illustrates the manufacturing steps for a three-cell batterypack. As shown in FIG. 15, an array of positive electrode activematerial layers 111 are formed on a panel A. An array of negativeelectrode active material layers 113 are formed on a panel B. On thepanel A, respective electrical connection points C0, C2 and C4 areprovided, which correspond to the electrical connection points C1, C3and C5 on the panel B. The panel A is laminated onto the panel B to forma three-cell in series configuration.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A thin film lithium-ion battery unit, comprising:a positive current collecting substrate; a positive electrode activematerial layer coated on an inner surface of the positive currentcollecting substrate; a negative current collecting substrate; anegative electrode active material layer coated on an inner surface ofthe negative current collecting substrate; a separator sandwichedbetween the positive electrode active material layer and the negativeelectrode active material layer; an electrolyte retained at least in theseparator, wherein the positive electrode active material layer, theseparator and the negative electrode active material layer constitute alaminated electric core; an outer conductive frame being spaced apartfrom the positive current collecting substrate and encompassing thepositive current collecting substrate with a gap formed therebetween,wherein the outer conductive frame and the positive current collectingsubstrate are coplanar, and wherein the outer conductive frame enclosesthe positive current collecting substrate along perimeter of thepositive current collecting substrate; a glue layer disposed in the gap;and a sealant layer disposed along a periphery of the laminated electriccore between the positive current collecting substrate and the negativecurrent collecting substrate so as to seal the laminated electric core,wherein the sealant layer is in direct contact with the laminatedelectric core, and wherein the glue layer is in direct contact with thesealant layer.
 2. The thin film lithium-ion battery unit according toclaim 1 wherein the outer conductive frame is an open-loop shaped frameand includes an opening for accommodating a positive tab that juts outfrom an edge of the positive current collecting substrate, wherein thepositive tab is coplanar with the positive current collecting substrate.3. The thin film lithium-ion battery unit according to claim 2 whereinthe outer conductive frame includes a protruding negative tab, whereinthe positive tab and the negative tab form a battery terminal pair, andwherein the protruding negative tab is coplanar with the positive tab.4. The thin film lithium-ion battery unit according to claim 1, whereinthe glue layer completely fills the gap, and wherein the glue layer iscoplanar with the outer conductive frame.
 5. The thin film lithium-ionbattery unit according to claim 1 further comprising a conductor layeris disposed adjacent to the sealant layer to electrically couple theouter conductive frame to the negative current collecting substrate. 6.The thin film lithium-ion battery unit according to claim 5 wherein theconductor layer is in direct contact with the sealant layer.
 7. The thinfilm lithium-ion battery unit according to claim 1 wherein the thin filmlithium-ion battery unit has a rectangular shaped outline.
 8. The thinfilm lithium-ion battery unit according to claim 1 further comprising acovering insulation layer that covers the outer conductive frame and thepositive current collecting substrate.